The invention relates to a method for interrogating control device data such as diagnostic data or status data via a diagnostic connection connected by communication lines with one or more control devices of a vehicle for carrying out the method.
In currently used vehicles, several electronic control devices are usually provided which fulfill specific operational and safety functions during operation of the vehicle. Such control devices are used, for example, for the open-loop and/or closed-loop control of the ignition, of the fuel supply, of the transmission, of the prevention of slippage, of the power, of the exhaust gas, of the braking process and the like. Such control devices are connected to one another in a known manner via a common communication line at which a diagnostic interface or a diagnostic connection is provided. It is intended that the functioning and the proper status of the individual control devices are to be checked via a test device connected to the diagnostic interface. To be able to communicate with the individual control devices, it is necessary to know the addresses of the individual control devices. It is also necessary to know whether a respective control device exists at all in the vehicle to be tested. These information items must either be known to the operator or they are stored in the test device, in which case, however, the test device would then only be usable for quite specific vehicle types. An automatic recognition of existing control devices and automatic access to these is not trivial problem for logistics and exceeds the capabilities of a simple manual test device. On the other hand, inputting respective addresses would be a very cumbersome method for communicating with the individual control devices which would require a large number of lists and tables to be updated. This is all the more so if the test device is to be used for a large number of different motor vehicle types and makes.